Using Field-Symbols in a user exit to change the importing parameter

Question

Please don't ask why but I need to use a user exit, changing the importing parameter.  I decided that I could do this using field-symbols.
Please excuse my ignorance but I have never used field symbols for something such as this.
Here is my goal:  Loop through an internal table (im_document-item).  When I find what I need I want to make a change to this line (not so hard if I am looping into a field symbol) and also append a line to the end of the table im_document-item.
I have the following so far:
  DATA: wa_item TYPE accit,
        wa_item_out type ACCIT_SUB.
FIELD-SYMBOLS: <document> type acc_document,
               <accit> TYPE ACCIT.
LOOP AT im_document-item ASSIGNING <accit> where saknr = '0000211000'.
* Modify the curent line
wa_item = <accit>
* Append a new line into table im_document-item.
ENDLOOP.
How can I use field-symbols to append a line to this table?  Please note that the table in question (im_document-item) is an importing only parameter.
Regards,
Davis

Answer 1

that will allow me to append an initial line with <accit> pointing to the line. Therefore I just have to modify <accit> and the new line will then have my changes?
Yep, that is exactly it.    So after the APPEND statement, simply fill the fields of the <accit>.
append initial line to im_document-item ASSIGNING <accit>.
<accit>-field1 = 'Blah'.
<accit>-field2 = 'Blah'.
Regards,
Rich Heilman